1. Field of the Invention
The present invention relates to an apparatus for changing capacity of a scroll compressor, and particularly, to an apparatus for changing capacity of a scroll compressor which is able to control an output capacity of the scroll compressor.
2. Description of the Background Art
Generally, a compressor is a device for changing mechanical energy into latent energy of fluid, and can be divided into reciprocating type, scroll type, centrifugal type and vane type.
Among those types, a scroll type compressor has a structure in which gas is sucked, compressed and discharged using a rotating body as in the centrifugal or vane type, unlike the reciprocating type using linear reciprocating movements of an opening/closing member.
FIG. 1 is a longitudinal cross-sectional view showing inner part of a conventional scroll compressor, FIG. 2 is a longitudinal cross-sectional view showing a seal member in FIG. 1, and FIG. 3 is a transverse cross-sectional view showing the seal member in FIG. 1.
As shown therein, the conventional scroll compressor comprises: a case 1 having a gas suction pipe (SP) and a gas discharge pipe (DP); a main frame 2 and a sub-frame (not shown) installed on upper and lower parts of an inner circumferential surface of the case 1; a driving motor 3 installed between the main frame 2 and the sub-frame; a rotary shaft 4 coupled on center part of the driving motor 3 so as to transmit rotating force of the driving motor 3; an orbiting scroll 5 having a wrap 5a of involute curve shape on upper part thereof, and installed on upper part of the rotary shaft 4 to be rotate eccentrically; and a fixed scroll 6 fixed on upper part of the main frame 2 and coupled to the orbiting scroll 5, and having a wrap 6a of involute curve shape therein to form a plurality of compression spaces P.
The inner part of the case 1 is partitioned into a suction pressure region (S1) and a discharging pressure region (S2) by a housing 7, and a middle pressure region (S3) is formed on a position communicating with the compression space P.
A gas suction hole 6b and a discharge hole 6c are formed on a side surface and on a center part of the fixed scroll 6, and a non-return valve 8 is installed on an upper surface of the fixed scroll 6 to prevent the discharged gas from flowing backward.
A tip seal recess 10 is formed on an end of the wrap 6a of the fixed scroll 6 so as to prevent the gas in the compression space (P) from leaking, and a seal member 11 is movably installed on the tip seal recess 10 (an end of the wrap of the orbiting scroll is same as that of the fixed scroll).
In addition, a clearance (C) for inducing gas is formed between an end surface of the seal member 11 and the end surface of the wrap 6a, and the gas of the compression space (P) is induced through the clearance (C), and the induced gas is induced into the tip seal recess 10.
Also, a controller which is able to change a capacity by controlling rotating number of the orbiting scroll is installed on one side of the orbiting scroll.
Hereinafter, in the conventional scroll compressor constructed as above, when electric power is applied to the driving motor 3, the driving motor 3 rotates the rotary shaft 4, and at that time, the orbiting scroll 5 coupled to the rotary shaft 4 is rotated as much as an eccentric distance.
At that time, the plurality of compression spaces (P) formed between the wrap 5a of the orbiting scroll 5 and the wrap 6a of the fixed scroll 6 are moved toward the center part of the orbiting scroll 6 gradually by the orbiting movements of the orbiting scroll 5, and thereby reducing the volume thereof.
The gas in the suction pressure region (S1) is sucked into the compression space (P) through the suction hole 6b continuously due to the volume reducing in the compression space (P), and the sucked gas is discharged into the discharging pressure region (S2) through the discharge hole 6c. 
At that time, in case that the compressor is normally operated, the gas in the compression space is induced into the tip seal recess 10 through the clearance C for inducing gas, and the induced gas compresses the seal member 11. The end surface of the compressed seal member 11 is adhered to the upper surface of the orbiting scroll 5 to prevent the gas leakage of the compression space.
Also, during low capacity operation, the rotating times of the orbiting scroll is controlled by the controller, and the suction gas is compressed and discharged in the same way described above.
However, in the conventional scroll compressor, since rotating speed of the orbiting scroll is reduced in order to change the capacity, the seal member is adhered tightly to the upper surface of the orbiting scroll due to the low pressure of the compression gas, and thereby, the compression gas may be leaked.
Also, according to the conventional art, an additional controller of high price should be disposed in order to control the deceleration of the orbiting scroll, and therefore, the fabrication cost is increased.